The present invention relates generally to apparatus for handling unitary loads, such as containers, concrete elements, plate-shaped objects and the like and, more particularly, to apparatus for handling unitary loads which include a prime mover, such as a power vehicle or the like, equipped with means for engaging and raising one end of the load from the base surface on which it rests.
The handling of large unitary loads, such as containers, is inconvenient, especially where available space in the vicinity of the load is limited. For example, the handling of containers at shipping docks where RO-RO vessels are loaded and unloaded can be quite difficult due to the limited available space.
Shipping containers are usually so large and heavy that it is not possible to move them by lifting only one of their ends. For this reason, several different techniques have been developed for handling containers in ports. One known technique utilizes a straddle carrier which comprises a large mobile crane having widely spaced wheels mounted on an inverted substantially U-shaped frame defining an open space which permits the crane to be driven over the container. The drawback of straddle carriers is that their use prevents containers from being loaded when they are situated in immediate side-by-side relationship with each other since the wheels of the straddle carrier require space on both sides of the container.
Trailers have been used to move containers or similar unitary loads. However, a separate crane or power truck is required to lift each container onto and from the trailer. This technique is not economical since the trailer itself constitutes a large, bulky piece of equipment which must be maneuvered through areas which are often quite limited. Additionally, the required number of trailers which must be kept on hand is often considerably larger than the cargo capacity of container carrying vessels thereby resulting in large expenditures which are often unnecessary.
Various arrangements have been suggested for overcoming the above-described disadvantages of conventional unitary load handling equipment. For example, load handling equipment is disclosed in Finnish Pat. No. 61,435 corresponding to U.S. Pat. No. 4,400,130, which comprises a lifting unit and a movable bogie unit connected to a prime mover by means of a telescopic frame. In operation, one end of a container is first lifted whereupon the bogie unit is moved under the container with the aid of the telescopic frame so that the bogie unit is positioned beneath the container in an area between the opposite end of the container and its center of gravity.